How often should a drain that has a plug in it be cleaned?

How often should a drain that has a plug in it be cleaned? we are a dry blending facility and do not use the drains on a regular basis. 

Hi, Kelseylouis.

Have you sampled your drain for environmental monitoring? If you have this sampled for a certain duration and observed to be in poor condition and with detection for micro of concern, then it could be a good starting point that cleaning frequency must be shorter than the duration of the sampling period. Verify this frequency and if turned to be with detection, rectify possible causes and may shorten the duration between cleaning frequency.

It will be difficult to suggest given lack of information, but whatever data you may have (if any), you may optimize it to justify decision.